3) 15/17-(в-3/17)=6/17
15/17-в+3/17=6/17
18/17-в=6/17
в=18/17-6/17
в=12/17
проверка 15/17-(12/17-3/17)=6/17, 15/17-9/17=6/17, 6/17=6/17
4) 29/43-(м+13/43)=5/43
29/43-м-13/43=5/43
16/43-м=5/43
м=16/43-5/43
м=11/43
проверка 29/43-(11/43+13/43)=5/43, 29/43-24/43=5/43, 5/43=5/43